U.S. patent application number 12/238284 was filed with the patent office on 2009-01-29 for apparatus for targeted delivery of additives to varying layers in gypsum panels.
This patent application is currently assigned to BPB plc. Invention is credited to Gerald D. BOYDSTON, Matthew J. CHOWNING, Michael P. FAHEY, Robert J. HAUBER, Mark E. HENNIS, Troy R. STUART.
Application Number | 20090025880 12/238284 |
Document ID | / |
Family ID | 36588254 |
Filed Date | 2009-01-29 |
United States Patent
Application |
20090025880 |
Kind Code |
A1 |
HENNIS; Mark E. ; et
al. |
January 29, 2009 |
APPARATUS FOR TARGETED DELIVERY OF ADDITIVES TO VARYING LAYERS IN
GYPSUM PANELS
Abstract
A multilayer gypsum board forming device, and a gypsum additive
delivery system in which additives are delivered to one or more
layers of a multi layered gypsum board panels, including engineered
polymers, includes at least one additive assembly connected in-line
with a first gypsum delivery receptacle for providing an additive
fluid feed into the stream of a first gypsum slurry being
transported through said first gypsum delivery receptacle for
homogenously adding an additive to the first gypsum slurry, and a
second gypsum delivery receptacle transporting a second gypsum
slurry, in fluid communication with the mixer providing the first
gypsum slurry, having a different set of characteristics from those
of the first gypsum slurry. At least one outer surface including a
polymeric compound or wax emulsion additive entrained therein
essentially encases the core gypsum within two facing layers.
Inventors: |
HENNIS; Mark E.; (Indian
Rocks Beach, FL) ; FAHEY; Michael P.; (St.
Petersburg, FL) ; HAUBER; Robert J.; (Lutz, FL)
; CHOWNING; Matthew J.; (Cody, WY) ; BOYDSTON;
Gerald D.; (Cody, WY) ; STUART; Troy R.;
(Cody, WY) |
Correspondence
Address: |
VANGELIS ECONOMOU;C/O IPHORGAN LTD
1130 LAKE COOK ROAD, SUITE 2400
BUFALLO GROVE
IL
60089
US
|
Assignee: |
BPB plc
Slough
GB
|
Family ID: |
36588254 |
Appl. No.: |
12/238284 |
Filed: |
September 25, 2008 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
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10968680 |
Oct 19, 2004 |
7435369 |
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12238284 |
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|
09997446 |
Nov 30, 2001 |
6878321 |
|
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10968680 |
|
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|
09875733 |
Jun 6, 2001 |
6524679 |
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09997446 |
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Current U.S.
Class: |
156/346 |
Current CPC
Class: |
B28B 5/02 20130101; Y10T
156/1062 20150115; E04C 2/043 20130101; B28B 19/0092 20130101; B32B
13/02 20130101; B32B 2260/021 20130101; B32B 2262/00 20130101; B32B
2419/00 20130101; B28B 5/027 20130101; B32B 2391/00 20130101; B28B
5/026 20130101; B28B 11/0845 20130101; B32B 13/04 20130101; B32B
2260/044 20130101 |
Class at
Publication: |
156/346 |
International
Class: |
B28B 19/00 20060101
B28B019/00 |
Claims
1-10. (canceled)
11. In a gypsum board forming device comprising a supply of
continuous sheet of material, a gypsum slurry mixer including a
gypsum delivery mechanism, disposed at least at one gypsum delivery
station for delivering said gypsum slurry onto said continuous
sheet, at least one additive assembly connected to an additive
fluid feed for adding a homogenous stream of an additive to the
first gypsum slurry in a first gypsum slurry transport receptacle,
a gypsum core delivery mechanism including a second gypsum slurry
transport receptacle, a sheet joining station for joining said
continuous sheet to said core gypsum, and a gypsum conveyor line,
having a belt with a surface for conveying formed gypsum board from
the sheet joining station, the at least one additive assembly
further comprising: an additive delivery port in fluid
communication with the additive fluid feed; a turbulator disposed
in-line with the additive fluid feed of at least one of the gypsum
delivery mechanisms, the turbulator comprising a fluid constrictor
having an outlet, the fluid constrictor outlet being disposed
adjacent the gypsum slurry stream being transported through the
first gypsum slurry transport receptacle.
12. In a gypsum board forming device according to claim 11 wherein
said fluid constrictor outlet disposed adjacent the gypsum slurry
stream being transported through the first gypsum slurry transport
receptacle is in fluid communication with the additive reservoir by
means of an in-line positive displacement pump.
13. In a gypsum board forming device according to claim 12 wherein
said additive comprises a wax emulsion.
14. In a gypsum board forming device according to claim 11 wherein
said additive comprises a wax emulsion.
15. In a gypsum board forming device according to claim 12 wherein
said additive comprises microfibers.
16. In a gypsum board forming device according to claim 11 wherein
said additive comprises microfibers.
17. In a gypsum board forming device according to claim 11 wherein
said additive comprises a material that can be solubilized or
dispersed in a liquid media.
18. In a gypsum board forming device according to claim 11 wherein
said additive comprises one or more materials taken from the group
consisting of polymers, boric acid, borates, intumescence-like
additives, surfactants, dispersants, retarders, potash, silicates,
starches, phosphates, perlite, alumina.
19. In a gypsum board forming device according to claim 11 wherein
said continuous sheet further comprises paper.
20. In a gypsum board forming device according to claim 11 wherein
said continuous sheet further comprises a mineral fiber facing
sheet.
21. In a gypsum board forming device according to claim 11 wherein
said continuous sheet further comprises a plurality of randomly
aligned glass reinforcing fibers pressed into a sheet.
22-26. (canceled)
27. In a gypsum board forming device having a supply of first sheet
material being continuously transported to a sheet joining station,
a gypsum slurry mixer for providing a continuous stream of first
gypsum slurry, a first gypsum delivery receptacle in fluid
communication with said gypsum slurry mixer for delivering a
continuous first gypsum slurry stream onto said sheet material, at
least one additive assembly connected inline with the first gypsum
delivery receptacle through an additive delivery port for adding an
additive into the first gypsum slurry stream so as to homogenously
mix said additive into said first gypsum slurry stream, comprising
at least one portion that extends into the receptacle and is in
said continuous stream of first gypsum slurry.
28. In a gypsum board forming device according to claim 27 wherein
said continuous sheet further comprises a pre-coated glass mat.
29. In a gypsum board forming device according to claim 27 wherein
said continuous sheet further comprises an inorganic glass mat.
30. In a gypsum board forming device according to claim 27 wherein
said at least one additive assembly further comprises a turbulator
disposed in-line with the first gypsum delivery receptacle and
being inserted through said additive delivery port.
31. In a gypsum board forming device according to claim 30 wherein
said turbulator further comprises a fluid constrictor having an
outlet, the fluid constrictor outlet being disposed adjacent the
gypsum slurry stream being transported through the first gypsum
slurry transport receptacle.
32. A gypsum board forming device comprising: a supply of
continuous sheet material being transported along a gypsum
manufacturing line, a gypsum slurry mixer having a first and second
gypsum slurry outlet, a first gypsum delivery receptacle, in fluid
communication with the first gypsum slurry outlet, the first gypsum
delivery receptacle for transporting a stream of a first gypsum
slurry from the gypsum slurry mixer and depositing said first
gypsum slurry onto said continuous sheet material, a second gypsum
delivery receptacle, in fluid communication with the second gypsum
slurry outlet, the second gypsum delivery receptacle for
transporting a stream of a second gypsum slurry from the gypsum
slurry mixer and depositing said second gypsum slurry onto said
continuous sheet material, at least one additive assembly connected
in-line to said first gypsum delivery receptacle for providing an
additive fluid feed into the stream of a first gypsum slurry being
transported through said first gypsum delivery receptacle for
homogenously adding an additive to the first gypsum slurry, a sheet
joining station for joining said continuous sheet to said second
gypsum slurry deposited on the continuous sheet material, and a
gypsum conveyor line having a belt with a surface for conveying
formed gypsum board, with sheets joined to the gypsum slurries from
the sheet joining station.
33. In a gypsum board forming device according to claim 32 wherein
said at least one additive assembly further comprises an additive
delivery port in the first gypsum delivery receptacle in fluid
communication with an inner conduit of the receptacle; and a
secondary mechanical mixing device disposed in-line with the gypsum
slurry stream for generating turbulation within the first slurry
stream to homogeneously mix said additive with the gypsum slurry
stream prior to deposition of the first gypsum slurry onto said
continuous sheet material.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This is a divisional of U.S. patent application Ser. No.
10/968,680, filed on Oct. 19, 2004, which is a continuation-in-part
of U.S. patent application Ser. No. 09/997,446 filed on Nov. 30,
2001, issued as U.S. Pat. No. 6,878,321 on Apr. 12, 2005, which is
a division of U.S. patent application Ser. No. 09/875,733, filed on
Jun. 6, 2001, issued as U.S. Pat. No. 6,524,679 on Feb. 25,
2003.
BACKGROUND OF THE INVENTION
[0002] 1. Field of the Invention
[0003] This invention relates generally to gypsum board and its
manufacture, and more specifically, relates to gypsum board having
at least one face or surface capable of receiving and adhering to
polymeric coatings and a manufacturing process permitting the
targeted delivery of the polymeric coatings to specified
locations.
[0004] 2. Background Art
[0005] Gypsum board, and its production, has received attention in
the building industry, and especially for providing an easily
worked building material the consistency of which is available for
general construction use. Desirable characteristics for gypsum
board also include a smooth working surface, consistent thickness
throughout, and the ability to provide finishing enhancements, such
as paint or other protective coverings, thereon.
[0006] Recent developments in the manufacture of gypsum board have
also added to the durability and versatility of the uses to which
gypsum boards may be put. For a fuller discussion of the
developments in the building board field is known as glass
reinforced gypsum (GRG) board, reference is made to the
aforementioned U.S. Pat. No. 6,524,679, commonly owned with the
present invention, and incorporated by reference has if fully
disclosed herein.
[0007] Manufacturing facilities for the production of gypsum board,
whether or not glass mats are utilized for the structural facings,
are capital intensive in the costs of space, equipment and in the
down time during which a gypsum board production line is
reconfigured. For production of a variety of gypsum board products,
for example, standard paper faced gypsum board, glass mat backed
board, etc., down time of the production line represents a
significant cost in the delay of production of gypsum board and in
time wasted by production workers who remain idle.
[0008] It has been further found that further finishing, e.g.,
painting, of a smooth gypsum board surface, is made easier because
the need for additional prefinishing steps, such as priming, etc.,
may be minimized.
[0009] In addition, gypsum products, e.g., wallboard, tile, block,
casts and the like, have relatively little resistance to water when
not modified by some chemical or physical modification to address
the problem of water absorption by the gypsum board. When gypsum
wallboard, for example, is immersed in water, the board may quickly
absorb a considerable amount of water, lose a great deal of its
integrity and structural strength, and distort or swell in
different places. Many attempts have been made in the past to
improve the water resistance of gypsum products by adding
waterproofing materials within the gypsum slurry. The most common
waterproofing material being used is a hydrophobic emulsion,
usually an emulsion comprising wax, paraffin, asphalt or a silicone
compound, e.g., silanes and siloxanes.
[0010] As can be expected, modification of gypsum slurry to render
it water resistant adds to the cost of gypsum production, both in
terms of the cost of the added substance, and in terms of the
additional equipment necessary to mix and deliver the water
resisting compounds to the gypsum slurry before application. Thus,
it has been found desirable to provide a gypsum board and
manufacturing process thereof which can be manufactured at
relatively high speed, has high structural integrity and strength
by virtue of using a mat of relatively low diameter fibers, and may
include in a face coating a polymeric additive material providing a
surface ideal for further finishing of the gypsum board, in
addition to a means for delivering the water resistant material
targeted to the location on the gypsum board where it would be most
useful, that is on the surface of the finished gypsum board
product. While the water resistant capability is desirable for all
of the gypsum layers in a gypsum board, it is now possible to
target specified layers of a multiplayer gypsum board that is made
in accordance with the aforementioned U.S. Pat. No. 6,524,679, and
other multilayer boards.
[0011] As a result of further development obtained through practice
and further consideration of the concepts disclosed and claimed the
aforementioned U.S. Pat. No. 6,524,679, it has been found
additionally desirable to provide a means for delivering specific
desired additives to a specified multilayer density layer of a
gypsum board panel, in order to obtain specified desirable
properties. For example, it has been found desirable to increase
the water resistance of the outer face surface of a glass mat
gypsum panel made in accordance with the teachings in the
aforementioned U.S. Pat. No. 6,524,679. Moreover, in accordance
with the teachings of that patent, the additives should only be
targeted to that layer, for example, the dense slurry layer, in
which it is desirable to provide the desired characteristic, so as
to avoid unnecessary cost and weight to the final board panel by
adding costly and sometimes denser additives to layers of the
gypsum board that will not provide as much benefit as those to
which the additives are targeted.
SUMMARY OF THE INVENTION
[0012] The present invention seeks to provide an improved gypsum
product and process therefor. In the present invention, contrary to
the prior art, the gypsum product is made by adding a hydrophobic
(that is, water repelling or resisting, the terms being used
interchangeably) substance, such as, but not limited to, paraffin,
wax, siloxanes and the like, in specified locations of the gypsum
board where the water repellent properties are most useful, that
is, at the surface and edges of the board. There is additionally
provided in accordance with an embodiment of the present invention
a method for providing water resistance to a predetermined surface
of a gypsum product, the method comprising adding a hydrophobic
substance to gypsum slurry that is directed to a specified location
on tile gypsum board.
[0013] Accordingly there is disclosed and claimed herein a method
of manufacture of gypsum board having fiber face sheets, comprising
the steps of providing a first gypsum slurry having a first
consistency continuously passing through a first gypsum slurry
transport receptacle, depositing a predetermined amount of said
first gypsum slurry onto at least a first continuous inorganic
fiber face sheet, transporting said first continuous fiber sheet
through a gypsum application station, providing a second gypsum
slurry having a second consistency and depositing said second
gypsum slurry onto said first fiber sheet and causing said second
gypsum slurry to be essentially evenly distributed over an upwardly
facing top surface of said first fiber sheet, providing a third
gypsum slurry having a third consistency and depositing it onto a
second of said continuous fiber sheets, said second inorganic fiber
sheet having top and bottom surfaces, thereby coating said top
surface of said second fiber sheet with said third gypsum slurry,
homogeneously mixing an additive into one of said first, second or
third slurries, prior to the steps of providing the gypsum
slurries, applying said second inorganic fiber sheet onto the
second gypsum slurry thereby sheathing said second gypsum slurry
within said first and second fiber sheets to form a wet gypsum
board product.
[0014] For use with an inorganic fiber, such as that disclosed in
aforementioned U.S. Pat. No. 6,524,679, the method of manufacture
of gypsum board having face sheets comprising inorganic fiber,
preferably randomly oriented inorganic fiber, comprises the steps
of depositing a predetermined amount of first gypsum slurry having
a first consistency onto at least one continuous sheet of randomly
aligned inorganic fiber material having random interstices between
the fibers by passing at least one continuous inorganic fiber sheet
through a gypsum application station, the station including two
applicator wheels through which pass the inorganic fiber sheet, so
as to cause the first gypsum slurry having a first consistency to
penetrate through the random openings between the inorganic fibers
and thereby to coat both top and bottom surfaces of the inorganic
fiber material with the gypsum having a first consistency,
directing the first inorganic material from the gypsum slurry
application station to a first forming plate, depositing a second
gypsum slurry having a second consistency on the first inorganic
fiber material and causing the second gypsum slurry to be
essentially evenly distributed over an upwardly facing top surface
of the first inorganic fiber sheet, applying a third gypsum slurry
having a third consistency to a second of at least one continuous
inorganic fiber sheets, and causing the third gypsum slurry to
penetrate essentially completely through random interstices in the
second inorganic fiber sheet, applying the second inorganic fiber
sheet onto the second gypsum slurry thereby sheathing the second
gypsum slurry within the first and second inorganic fiber sheet to
form a wet gypsum board, passing the wet gypsum board through a
board forming station having a lower forming plate and an upper
forming plate, the upper forming plate comprising sections and
defining at least one predetermined angle relative to the lower
forming plate, the vertical separation between the lower plate and
at least one section of the upper plate having a predetermined
vertical dimension substantially equal to the desired thickness of
the manufactured gypsum board. Alternatively, a forming wheel may
be utilized to provide gypsum board having a predetermined
thickness. Optionally, an edger bar may be used to smooth and
otherwise complete the surface finish of the gypsum board. In a
second embodiment, the method includes adding one or more polymeric
additives to the gypsum slurry of one or both surfaces.
[0015] In another embodiment of the present invention, a multilayer
gypsum board comprising a first layer of set gypsum comprising a
first layer of a mixture of set gypsum having an outer surface and
at least one polymeric compound entrained within the set gypsum,
and being impregnated within a thin sheet of randomly aligned
inorganic fibers, the outer surface of the sheet being essentially
encased within the set gypsum and polymeric compound, a second
layer comprised of set gypsum, the set gypsum in the second layer
being of a lower density than the set gypsum in the first layer;
and a third layer having an outer surface comprising set gypsum
impregnated with a second thin sheet of randomly aligned inorganic
fibers, the outer surface of the third sheet being essentially
encased within the set gypsum of the third layer; the set gypsum in
the first being integrally bonded to the gypsum of the second layer
and the set gypsum in the second layer being bonded integrally to
the gypsum in the third layer.
[0016] One feature of the invention is the use of a turbulator
mechanism in the additive delivery assembly. In a gypsum board
forming device comprising a supply of continuous sheet of material,
a gypsum slurry mixer including a gypsum delivery mechanism,
disposed at least at one gypsum delivery station for delivering the
gypsum slurry onto the continuous sheet, at least one additive
assembly connected to an additive fluid feed for adding a
homogenous stream of an additive to the first gypsum slurry in a
first gypsum slurry transport receptacle, a gypsum core delivery
mechanism including a second gypsum slurry transport receptacle, a
sheet joining station for joining the continuous sheet to the core
gypsum, and a gypsum conveyor line, having a belt with a surface
for conveying formed gypsum board from the sheet joining station,
the additive assembly including an additive delivery port in fluid
communication with the additive fluid feed, a turbulator disposed
in-line with the additive fluid feed of at least one of the gypsum
delivery mechanisms, the turbulator comprising a fluid constrictor
having an outlet, the fluid constrictor outlet being disposed
adjacent the gypsum slurry stream being transported through the
first gypsum slurry transport receptacle.
BRIEF DESCRIPTION OF THE DRAWINGS
[0017] FIG. 1 is a diagrammatical, cross-sectional view of the
gypsum board forming station according to the present
invention;
[0018] FIG. 2 is a detailed, cross-sectional, diagrammatical view
of the vibrator sub-assembly shown in FIG. 1;
[0019] FIG. 3 is a detailed, cross-sectional, diagrammatical view
of FIG. 1, showing the top sheet sub-assembly according to the
present invention;
[0020] FIG. 4 is a schematic illustration of the structural
elements used to provide the emulsion mixing and delivery system to
the desired layers of the gypsum board;
[0021] FIG. 5 is a detailed plan view of an embodiment of the
invention;
[0022] FIG. 6 is a detailed perspective view of a single one of the
inventive additive delivery systems; and
[0023] FIG. 7 is a perspective partially cutaway or unassembled
view of the inventive system shown in FIGS. 5 and 6.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0024] In the diagrammatical, cross-sectional illustration of FIG.
1, the board forming station 10 of an inventive embodiment of the
inventive plant is shown. Although illustrated in cross-section,
the station 10 is shown diagrammatically to clearly depict the
separate elements in relation to each other. Modifications to the
arrangement are possible and distances between the separate
elements are not to scale for simplicity of illustration, but a
pragmatic and efficient arrangement will come to mind to a person
having ordinary skill in the art.
[0025] The inventive plant 10 comprises a supply roll 12 that
provides feed of a continuous sheet of facing material that, in the
arrangement shown, defines a bottom-facing sheet 14. The supply
roll 12 may feed out a sheet comprising any conventional material
used in gypsum boards, for example, paper or paper board, but for
purposes of the present invention, the material of bottom facing
sheet 14 preferably comprises a mat of long inorganic, e.g., glass,
fibers which will be more clearly described below with reference to
the formation of the inventive gypsum board product, when the
inorganic fibers comprise a glasso-glassive fiber, the products
being, sometimes referred to herein as glass reinforced gypsum
("GRG") boards.
[0026] The supply roll 12 pays out the continuous bottom facing
sheet 14 over a first forming table 16, having an upwardly facing
surface 18, provides a working surface for further processing of
the bottom facing sheet 14. The first forming table 16 also
provides a support for creaser wheel assembly 20, disposed athwart
the surface 18. The sheet 14 may be extracted from the supply roll
12 by motion of the sheet being pulled through the board forming
station 10 by the belt line, as will be described. The two creaser
wheels are vertically disposed within the creaser wheel assembly
20, one set of wheels 22 above the bottom facing sheet 14 cooperate
with a second set of wheels, referred to as the wheel anvil 22',
below the sheet 14. The creaser wheels 22, 22' rotate on axles and
produce partially cut edge creases on the sheet 14 adjacent to each
of the longitudinal edges of the bottom-facing sheet 14. The edge
creases are spaced to allow varying fold thicknesses and to cause
the edges to turn upwardly so as to retain slurry poured onto the
bottom-facing sheet 14 downstream of the creaser wheel assembly 20,
as is described below.
[0027] A continuous mixer 30, accepting raw materials, i.e. stucco,
plaster, gypsum (in powder form), water and other additives,
through one or more inlets, one of which inlets 32 is shown in FIG.
1. The mixer 30 provides a mixing capacity that formulates a
desirable density of wet gypsum slurry by, for example, rotating a
mixing blade (not shown) via a drive shaft 33. Because it is a
desirable feature for this invention to produce a multi-layer
gypsum board, the mixer 30 may comprise separate mixing chambers
(not shown in FIG. 1) for providing separate, and different slurry
mixtures. A continuous mixer, such as that utilized in this
invention, is described and illustrated in commonly-owned U.S. Pat.
No. 5,908,521, which is incorporated by reference as if fully set
forth herein.
[0028] The continuous mixer 30 thus provides several outlets for
gypsum slurry each having varying desirable characteristics
depending on the function of the slurry layer for which any
Specific outlet is producing gypsum slurry. Each outlet includes an
output control for controlling the amount of gypsum slurry
permitted to flow through the outlets and into the gypsum board
forming plant. The control may be one or more slurry delivery
mechanisms, as described in aforementioned U.S. Pat. No. 5,908,521,
which have controlled variable delivery speeds so that only the
desired amount of gypsum slurry is pumped through the outlets.
[0029] Referring again to FIG. 1, mixer 30 comprises a first slurry
outlet 34, controllable by a control device 36, that allows for the
continuous flow of a slurry mixture having desirable
characteristics, as described in aforementioned U.S. Pat. No.
5,908,521. In this embodiment, mixer 30 is set to provide two types
of slurry. Control device 36 delivers a denser gypsum slurry
mixture that is ultimately utilized adjacent the facing of the
completed gypsum board, as will be described below.
[0030] The end of the slurry outlet 34 extrudes the gypsum slurry
directly onto the bottom-facing sheet 14, which is continuously
moving over the surface 18 of forming table 16. Slurry outlet 34
preferably comprises a rubber boot, but other types of outlets may
be used, for example flexible hoses or piping. Preferably, the
gypsum slurry 38 is poured onto the upwardly facing surface of the
sheet 14 at a position where it is supported by the forming table
surface 18, and a predetermined amount of dense gypsum slurry is
deposited over the continuously moving sheet 14 so as to coat the
internal surface of bottom face sheet 14. It should be noted that
this upwardly facing internal surface of sheet 14 is normally
destined to be an inner surface of the bottom-facing sheet 14, and
will be facing inwardly from the board surface when the gypsum
board is fully formed. To ensure that the dense gypsum slurry 38 is
evenly spread out over the top surface of the bottom face sheet 14,
a set of roller wheels 40, 42, also referred to herein as roll
coaters 40, 42, are positioned again vertically over and under the
sheet 14. The wheels 40, 42 can rotate in forward or reverse
directions.
[0031] One advantage and benefit which derives from use of rotating
roller wheels 40,42 is that in addition to providing a smooth,
evenly spread surface coating over the mat comprising the bottom
facing sheet 14, the dense slurry layer 38 deposited on the inner
mat surface is forced, by the top roller wheel 40, to extend
through the sheet 14 and to form a structurally integral surface.
The surface layer of gypsum slurry 38 may be modified to include
additives, such as an engineered polymer, to provide structural
strength and load carrying capability to the gypsum board product.
As will be described, the optional polymer additive may also
present a polymer matrix that provides a water impervious surface
having desirable performance characteristics, such as, plastic
sheathing, or water repelling, properties so as to expand the
possible uses of the gypsum board products to both indoor and
outdoor use.
[0032] In a preferred embodiment of the invention, the material
comprising the bottom-facing sheet 14 is a mat of randomly aligned
mineral, e.g., glass, fibers, having an average fiber diameter of
13-16 .mu.m (0.005-0.0065 inches), and including a binder to hold
the glass fibers in the form of a glass fiber mat having a
desirable thickness. Such glass fiber mats are known for use in the
production of gypsum board, for example, see aforementioned U.S.
Pat. No. 6,524,679, No. 4,378,405 and WIPO Publication No.
WO9809033 (European Patent No. EP 0 922 146). Use of a mineral
fiber mat, which is porous to water generally, provides added
structural strength to the gypsum board. The porous nature of the
mineral fiber mat also permits gypsum slurry to penetrate through
the pores between the mineral fibers and to permeate so as to cover
both the top surface and through slurry penetrating the bottom
surface of bottom facing sheet 14 because of slurry penetration.
Thus, as the bottom facing sheet 14 passes through the roll coaters
40, 42, the unset higher density gypsum 38 is coated over the
mineral fibers and is forced in the roll coating process to
penetrate through the bottom facing sheet 14 and coat each of its
top and bottom surfaces with an unset denser gypsum layer 38.
Ideally, the high-density gypsum 38 is forced to penetrate 100%
through the glass mat sheet 14, although manufacturing tolerances
may permit penetration of approximately 95-98%.
[0033] In a preferred form, the roll coaters 40, 42 cause
penetration of the unset denser gypsum slurry 38 to coat the bottom
surface of the glass mat bottom sheet 14. This bottom surface of
the bottom-facing sheet 14 will ultimately become the facing
surface of the completed gypsum board products. Preferably, the
unset gypsum slurry 38 is caused to form a dam 39, which then
impregnates a continuous layer of unset gypsum through to the
bottom surface of the glass mat 14 to form a dense slurry gypsum
layer having a thickness that is in a range from approximately 0.01
to 2.0 mm, as measured from the outermost surface of glass mat 14.
Although penetration of the slurry 38 may not result in a
continuous layer having a discrete thickness, nevertheless the
process preferably will result in each of the glass fibers,
comprising the glass fiber mat 14, in being coated on its surface
so that very few or no exposed uncoated glass fibers remain.
[0034] The speed of rotation of the rollers 40,42 may be adjustable
depending on the viscosity of the density of gypsum slurry 38, the
speed of linear travel of the glass fiber mat 14 and the amount of
the gypsum slurry 38 to be applied to the mat 14. In effect, the
roll coaters 40, 42 serve to deliver the slurry 38 through the
small random openings between fibers of mat 14 and deposit the
material on the top of the fabric web in greater or lesser amounts,
as desired, filling the openings and coating both the bottom face
as well as the top face of mat 14.
[0035] Although the roll coaters 40, 42 are shown rotating in the
direction of travel of the bottom facing sheet 14, it is possible,
and in some embodiments of this invention, desirable to have the
roll coaters rotate in the opposite direction from that shown in
FIG. 1. In such case, a mechanism such as a forming belt line,
disposed downstream of the roll coaters 40, 42, described below, is
utilized to provide a motive force for pulling the bottom facing
sheet 14 through the gypsum board forming station 10, even against
the reactive forces produced by counter-rotating coater rolls. Of
course, alternatively, other means may be utilized at different
locations in the processing production line to provide the motive
force for moving the sheet 14 through the station 10, for example,
another set of rollers downstream (not shown) that pull the mat 14
toward the right. It should be noted that the gypsum slurry layer
on the top surface of bottom facing sheet need not be absolutely
level or completely even since subsequent steps in the process may
provide additional smoothing opportunities, as will be described
below.
[0036] Gypsum board with mineral fiber facing sheets may be
produced in multiple layers, including, but not limited to, a
strong, more dense upper and lower surface layers and a less strong
and less dense middle layer or core. The layered structure is
advantageous as it allows the gypsum board to have a reduced
weight, without sacrificing the composite structural strength of
the final gypsum board product. Thus, and in accordance with the
teachings of aforementioned U.S. Pat. No. 5,908,521, the continuous
mixer 30 is configured to provide a second, less dense gypsum
slurry, referred to as core gypsum slurry 44 or simply slurry 44,
which comprises the bulk of the material in the finished gypsum
board products. The core gypsum slurry 44 is pumped out of the
mixer 30 by a control device 46 and through an outlet 48, which may
comprising a rubber boot or hose. A continuous layer of the unset
slurry 44 is caused to form onto the laterally moving combination
bottom facing sheet 14 and layer of dense slurry 38.
[0037] The core slurry 44 may comprise a different composition of
constituent material than the dense gypsum slurry 38, for example
by the addition of filler or strengthening additives, as is known,
or may simply comprise the same constituent elements but may have a
lighter or less dense consistency because the gypsum slurry 44
contains foaming materials therein, which are not added to the
dense slurry 38. It is known that a longer mixing time for the
unset gypsum causes more of the entrained air bubbles, sometimes
referred to as foaming, to reach the surface of the unset gypsum
and thus to be removed from the unset gypsum slurry material. It is
the greater amount of air, entrained as miniscule air bubbles,
which gives rise to the lighter, less dense core gypsum slurry
44.
[0038] Gypsum slurry, and especially gypsum slurry that has been
modified with polymer additives, has adhesive characteristics in
its wet state that present some difficulty in handling.
Accordingly, a film coating 43 is preferably provided on at least
one of the roll coaters, preferably roll coater 42, which allows
for easier continuous separation of the coater wheel surface from
the surface of the wet gypsum surface while simultaneously
depositing the majority of the gypsum slurry 38 on the mat of sheet
14. Materials for such a film coating surface include appropriate
polymers, such as a Teflon.RTM. coating, that are capable of
providing a firm surface yet avoiding gypsum slurry adhering or
clinging to the surface of the roll coater wheels.
[0039] Another important reason for providing a denser slurry
layer, in conjunction with a lighter core slurry layer in the
gypsum board, is that the boundary between the dense slurry layers
38, and the core slurry layer 44 provides an inhibiting barrier
that serves to control and inhibit the migration of the polymer
additives from the surface dense slurry layer 38 to the core slurry
layer 44. This migration is most likely to occur during the
conventional heat rendering process, described below, used for
drying the finished board product. The resulting board product is
rendered better equipped to retain the polymer additives in the
surface dense slurry layer 38, which thus form a better, more
uniform polymer matrix base or "root system" for co-polymer
formation with finishing products, as is described below.
[0040] As the dense gypsum layer 38 dries and cures, the polymer
additives entrained therein migrate toward and through the
underlying fiber facing sheet 14 and the migration may extend into
the core slurry layer 44 in the form of tendrils or roots that
provide for a greater integrity in the bond formed between the core
gypsum layer 44, the fiber sheet 14 and the overlying dense slurry
layer 38. Moreover, because the lighter gypsum layer 44 includes an
entrained foam, and the dense slurry layer 38 does not, the
penetration of the additive materials is deeper into the layer 44.
This bonding produced by the impregnated additive polymeric
material improves matrix formation, ultimately improving the
surface hardness and structural integrity of the finished gypsum
board, and provides a strong outer shell to the board and also
improves the load bearing capacity, contributing to its
flexibility.
[0041] Referring again to FIG. 1, after passing through the roll
coaters 40, 42, the bottom facing sheet 14 passes onto a second
forming table 50 having a horizontal forming surface 52. Although
the first forming table 16 and second forming table 50 are shown as
separate tables in the diagrammatic rendition of FIG. 1 it is
possible and in certain cases preferable, that the forming table
comprises one elongated table (not shown) with several cutout
portions within which, for example, the creaser wheel assembly 20,
or the roll coaters 40, 42 and vibrators, are mounted.
[0042] To facilitate the transport of the bottom-facing sheet 14,
including the weight of the dense slurry 38 and core slurry 44, a
nonstick table deck 59 is disposed over the surface 52 of table 50.
Referring now to FIG. 2, which is a detailed view of FIG. 1, an
upwardly facing surface 60 of table deck 59 provides a working
surface for the production of gypsum board. Preferably, the table
cover comprises a smooth, non-stick material, such as stainless
steel, an elastomeric material, e.g., rubber, or a polymeric
material, e.g., Formica.RTM., and is of sufficient structural
strength to support the moving weight of the slurry 44 deposited on
the table 50.
[0043] As is evident in the detailed cross-sectional view of FIG.
2, the table deck 59 rests directly on surface 52 of table 50, so
that as the core slurry 44 is deposited on the bottom facing sheet
14, the weight of the slurry 44 places downward pressure on the
sheet 14, resulting in flattening of the under surface of the sheet
14 against the surface of the table deck 59. However, because of
the smooth, non-stick characteristics of the table deck 59, the
bottom facing sheet 14 and slurry 38, 44, freely traverse over the
forming tables, as described below.
[0044] The cross-sectional view of FIG. 1 also does not show the
width of the outlet spouts 34 and 48. Various known configurations
may be utilized, including an elongated spout that is disposed
transversely to the direction of board travel. Such spouts may
output a sheet of gypsum slurry across the width of the mat 14.
Alternatively, a tubular spout attached to a rubber boot (as shown)
deposits a continuous stream of gypsum slurry onto the glass fiber
sheet 14. That gypsum slurry stream may then be spread out, before
reaching the roll coaters 40, 42, to provide a smooth Surface over
the sheet 14 by, for example, diagonally angled vanes (not shown)
or by specially constructed rollers or a dam that spread the gypsum
slurry from the center toward the edges of bottom sheet 14. The
exact shape of the spouts is not considered to be critical to this
invention, as long as the function is achieved of evenly spreading
the gypsum slurry over the entire width of the mat of both the
bottom and top sheets.
[0045] The unset, less dense core gypsum slurry 44 is deposited on
the penetrated bottom facing sheet 14 at or adjacent a third
forming table 56, having a top surface 58, for supporting the
combination of penetrated mat 14 and slurry 44. An opening 62
between the second forming table 50 and third forming table 56
provides a space for disposing a first deck vibrator 64, and
another opening 66 provides for mounting a second deck vibrator 68
between the third forming table 56 and a fourth forming table 70,
having a top surface 72. Such vibrators are described in U.S. Pat.
No. 4,477,300, which is incorporated by reference herein.
[0046] As shown more clearly in the detailed view of FIG. 2, the
table deck 59 extends between the first and second forming tables
50, 56 over the opening 62, and also between the third and fourth
forming tables 56, 70 over the opening 66. Because each of the
tables 50, 58, 70 are disposed so that their surfaces 52, 58, 72
are coplanar, the table deck 59 mounted onto the table is
vertically fully supported across essentially the full length of
the gypsum board forming station 10, i.e., across the full length
defined by second to fourth forming tables 50, 56, 70.
[0047] Shown in FIG. 2, deck vibrators 64,68 each comprise rolls
74, which are mounted immediately adjacent sections of the table
deck 59 covering the upper portion of the respective openings 62,
66. Each of the deck vibrator rolls 74 are mounted to rotate around
axles 76, both extending horizontally in a direction transversely
to the direction of travel of the board production line. Each of
the rolls 74 has a diameter that is just slightly less than the
radial distance between each axis 76 and the bottom surface 62',
66' of the table deck 59 covering the respective openings 62,
66.
[0048] Each deck vibrator 64,68 further comprises a plurality of
bumps 78 which extend radially beyond the outer surface 79 of the
deck vibrator rolls 74. Bumps 78 extend longitudinally along the
surface 79 of the rolls 74 in a direction parallel to the axis 76.
As the deck vibrator rolls 74 rotate about axis 76, the bumps 78
routinely strike the underside surfaces 62', 66' of the table deck
59, which momentarily lifts the table deck 59, together therewith
the bottom facing sheet 14 and slurry 38, 44, combination, which
agitates the slurry resting on sheet 14. Such agitation causes the
slurry 38 to even out over the upper surface of the penetrated mat
14 and also causes the slurry 44 to more completely permeate
through and bond with the denser slurry 38 located on the upper
surface of the bottom facing sheet 14.
[0049] Another feature provided by the deck vibrators 64,68, is the
"kneading out" of larger entrapped foam air bubbles from the bottom
surface of the bottom facing sheet 14. As the bottom-facing sheet
14 passes over the openings 62, 66, the denser slurry 38, which has
penetrated through the mat of bottom facing sheet 14, is still
unset and continues to have entrained air bubbles within the gypsum
slurry and adjacent bottom sheet surface. Vibration from the deck
vibrators 64, 68, causes these foam bubbles to reach the surface
and exit from within the penetrated gypsum slurry 38, thus
resulting in a smooth outer surface of the completed gypsum board
when the manufacturing process is completed, as in aforementioned
U.S. Pat. No. 4,477,300.
[0050] Completion of the smoothing operation of the slurry 44,
resulting in an essentially planar combined bottom facing sheet 14
and core slurry 44 is further facilitated by a forming plate in the
top and bottom sheet joining station 80 (FIG. 1), disposed
downstream, i.e., toward the right as seen in FIG. 1, of the deck
vibrators 64, 68. The forming plate assembly of sheet joining
station 80 operates in conjunction with a top facing sheet 114
formed by the sheet coating station sub-assembly 110 having similar
elements to those in the main production line that form the
bottom-facing sheet 14.
[0051] Top-facing sheet 114 is comprised of a sheet or mat of
randomly aligned mineral fibers, such as glass fibers, and is
unrolled from a supply roll 112, similar to the supply roll 12.
Similar elements to those used for the production of bottom facing
sheet 14 are identified by like numerals in the 100 series,
utilizing the same two last digits as those identifying the like
elements in the production of the bottom sheet 14. Supply roll 112
pays out a continuous top facing sheet 114, which, in the completed
gypsum board, will be adjacent the inner facing surface of the
gypsum board product subsequently used in wall construction.
[0052] As shown in FIG. 1, the top facing sheet 114 may require
feeding through various loops around, for example, rollers 102, so
as to avoid interference of the main production line by the
operation of top sheet sub-assembly 110. Top sheet sub-assembly 110
directs the top facing sheet 114 over a top sheet forming table 116
having an upwardly facing surface 118.
[0053] The continuous mixer 30 further comprises a slurry outlet
134 being controllable by a control device 136 providing a
continuous stream of denser gypsum slurry 138 to the sub-assembly
110 for deposit onto the top facing sheet 114, as shown. A detailed
cross-sectional view of the top sheet production station portion of
sub-assembly 110 is illustrated in FIG. 3, and reference is now
jointly made to FIGS. 1 and 3. Although in FIG. 1, the preferred
embodiment of two separate slurry controllers 36, 136 are shown for
supplying two different slurry mixtures 38, 138, for respectively,
the bottom facing sheet 14 and the top sheet 114, it may be
desirable to have one mixer discharge leading to dual controllers
for controlling the discharge of two or more outlets, similar to
that described in aforementioned U.S. Pat. No. 5,714,032.
Alternatively, a single controller (not shown) may be used with the
discharge outlets having individual valves enabling variable flow
of gypsum slurry that is controllable for each outlet spout
depending on the operational needs of the board production
process.
[0054] Shown in FIG. 1, are separate controllers 36, 46, 136, each
for controlling the output of a single outlet, i.e., dense gypsum
slurry outlets 34, 134, or core slurry outlet 48. The configuration
of the continuous mixer 30 provides separate mixing chambers, each
attached to, and feeding gypsum slurry to, a separate outlet, which
provides a specific type of gypsum slurry, as needed. Customization
of the slurry provided to each of the outlets 34, 48, 134 thus
enable a gypsum board line operator to provide different slurries,
having desirable characteristics, to the location in the
manufacturing line where needed. For example, an outlet, such as
outlet 34, may be required to provide a denser gypsum slurry, such
as slurry 38. The slurry may be desired to include specified
additives, for example, a polymeric compound, which forms a matrix
with the set gypsum after it sets, so as to provide a suitable
surface for further finishing, as will be described below. However,
if it is only necessary for the front facing surface to have such a
surface, then using the embodiment shown in FIG. 1 provides the
option to include the additive in only the dense gypsum slurry 38,
pumped from controller 36, but not to include such an additive in
the slurry 138, which will end up on the inner, back side of the
gypsum board during construction. Alternatively, the gypsum slurry
138 is denser than the core slurry 44, and may have an identical
consistency as that of the slurry 38 coating the bottom facing
sheet 14.
[0055] Referring again to FIGS. 1 and 3 showing the top sheet
slurry coating station 110, the dense gypsum 138 is deposited on
the top facing sheet 114, comprised of a mat of glass fibers, which
is moving in the direction shown by arrow A, past the surface of
the top sheet slurry table 116. The top sheet is moving essentially
at the same rate as that of the bottom facing sheet 14 traveling
over forming table 16. The gypsum slurry 138 is denser than the
core slurry 44, and may have an identical consistency as that of
the slurry 38 coating the bottom-facing sheet 14.
[0056] The top facing sheet slurry coating station 110 comprises a
short forming plate 116, similar to the forming table 16, with the
exception that the linear dimension of plate 116 is much shorter,
having a sufficient length to achieve deposition of the gypsum
slurry 138 and to spread out the slurry over the surface of the
moving top facing sheet 114 between the lateral edges of the
continuous sheet 114. To assist in the process of spreading the
gypsum slurry 138 over the surface of sheet 114, one or more
pneumatic table vibrators, such as vibrator 148, may be included to
vibrate the surface 118 of the table 116.
[0057] Applicator wheel 140, having a cylindrical surface 142,
rotates about an axle 144, which axle 144 extends transversely to
the direction of travel of the sheet 114. The vertical and
horizontal disposition of axle 144 is important in obtaining the
desired result of sheet 114 being fully impregnated with the dense
slurry 138. As shown in FIG. 3, axle 144 is disposed linearly at a
very short distance past the edge 117 of table 116. The axle is
vertically disposed just slightly less than the radius of wheel 140
above the table surface 118 so that the applicator wheel 140
extends into the space under the plane defined by the table surface
118. As is shown in FIG. 3, during production the applicator wheel
140 puts downward pressure on top facing sheet 114, which sheet is
deflected some slight distance from its linear path followed across
the table surface 118.
[0058] The dense gypsum slurry 138 being deposited on the moving
top facing sheet 114' produces a slurry concentration at a dam 139,
comprised of excess dense slurry 138, which collects in the
constricted space between the applicator wheel 140 and the top
facing sheet 114. The size of dam 139 can vary, depending on the
desired characteristics of the resulting impregnated top facing
sheet 114' that is produced by the top sheet coating station 110.
For example, if a greater degree of coating is desired to provide
greater structural strength of the gypsum board, then the size of
the dam 139 may be adjusted so that a greater amount of dense
gypsum slurry is impregnated into the interstices between the
mineral fibers of the mat comprising top facing sheet 114. For
purposes of distinction, top facing sheet 114 is designated as
impregnated top facing sheet 114' after impregnation by the dense
slurry 138.
[0059] Working in conjunction with the applicator wheel 140 is
downwardly curved transversely extending directional plate 113,
upon which the sheet 114 impinges as it exits from contact with the
applicator wheel 140. The directional plate 113 is preferably
mounted so that the apex 115 is adjacent or within the plane
defined by the surface 118. This positioning causes the sheet 114
to be placed into tension as the applicator wheel 140 pushes the
sheet 114 downwardly from the plane, which disposition assists in
the penetration of the gypsum slurry 138 through the mat of sheet
114. To inhibit the formation of slurry 138 on the surface 142 of
applicator wheel 140, an appropriate thin film coating 143,
comprising, for example, a Teflon.RTM. coating, may be optionally
disposed on the surface of wheel 140, similar to the coating 43 of
roll coater 42 described above.
[0060] The top sheet 114', impregnated with the dense gypsum slurry
138, is directed from the applicator wheel 140 to a second roller
wheel, the transition roller wheel 104, having an axle 144' that is
parallel to axle 144. The transition roller wheel 104 is in the
general path and in the plane defined by the surface 118, and its
function is to change the direction of travel of the top facing
sheet 114' so as to render the top surface of the sheet to become
the bottom surface, and vice versa. That is, the surface of the top
facing sheet 114 that was on the bottom adjacent the surface 118,
becomes the top surface and the sheet 114' is ready for delivery to
and joining over the core slurry 44, as is described below.
[0061] The sheets 14, 114' are joined at a sheet joining station 80
(FIG. 1) that is described in more detail in aforementioned U.S.
Pat. No. 6,524,679, and the remainder of the discussion in that
patent relating to the board forming structure and methods will be
omitted for brevity, except for the following paragraphs describing
the ratio of the polymer additives to the gypsum.
[0062] It has been found and it is a feature of this invention that
addition of a specific group of polymer additives, when mixed into
the dense slurry 38, provides a number of these characteristics
that provide the defined advantages. The solid polymeric compounds
are dissolved in water in almost any desirable proportion, but
preferable is a solution of about a 45% polymeric solids content
diluted in water. In a preferred embodiment, the polymeric solution
is pumped to the predetermined controller(s), for example
controllers 36, 136, and added to the mixture of dense slurry 38,
138 mixed in each chamber of mixer 30. The dense slurry controllers
36, 136 then supply the dense slurry 38, 138 through outlets 34,
134 directly to the applicator roll coater wheels 22, 22' as
needed, to provide an increased physical surface strength to the
completed gypsum board, so as to significantly exceed standard
board specifications.
[0063] Ideally, the polymer additive in the gypsum slurry solution
enhances the bonding strength also between the core slurry 44 and
the outer surface dense slurries 38, 138 and between the dense
slurry that extends across and through the mats of the glass fiber
facing sheets 14 and 114'. The polymer is thought to generate a
polymer matrix that extends from the junction of the lower density
core slurry and into the dense slurry layers 38, 138, which have
penetrated through the sheets 14, 114, and to extend to the surface
of the gypsum board. The polymer matrix is effectively embedded
within the gypsum base and provides a coalescing surface upon which
further finishing can be based, for example, painting or a water
impervious acrylic cover, that may be added at this stage of the
finishing process, for example, by spray coating.
[0064] The surface texture of the front face of the completed
gypsum board includes the polymer, which as a part of the
underlying matrix, presents a smooth dense layer of gypsum to which
other polymeric, e.g., acrylic, compounds can adhere. As the
polymer layer cures, for example, in the drying process, it hardens
to provide a stiff surface capable of retaining a load. The surface
having the polymer additive, reduces chalking, improves water
resistance and provides specific sites for chemical adhesion by
other polymers. The composition of a water resistant or impervious
coating can comprise one or a combination of the following
polymeric compounds: polyacrylamide, polymethylacrylamide,
polyvinyidene chloride (PVDC), Nylon.RTM., polyvinylchloride (PVC),
polyethylene, cellulose acetate, polyisobutylene (Butyl Rubber),
polycarbonate, polypropylene, polystyrene, styrene, butadiene,
styrene butadiene copolymer, polychloroprene (Neoprene.RTM.),
tetrafluoroethylene fluorocarbon and fluorinated ethylene propylene
(Teflon.RTM.), natural rubber, poly (2,6 dimethyl pentene oxide),
poly 4, methyl pentene-1 and polydimethyl siloxane.
[0065] Preferably, the polymer is in solution with the water and
can be in a range of from about 1% to about 99% solution, but a
preferable range is from about 40% to 50% polymer, and most
preferably is about 45% polymer by weight. Preferably, the polymer
solution is pumped into the controllers for delivering gypsum
slurry to the front and back face sheets 14, 114' at a supply rate
between about 190 cm.sup.3 (0.05 gallons) per minute to about 0.019
m.sup.3 (5.0 gallons) per minute and a preferred rate of between
190 cm.sup.3 (0.1 gallons) to 0.004 m.sup.3 (1.0 gallons) per
minute. The actual delivery rate may vary depending on the speed of
the board production line and other manufacturing
considerations.
[0066] The surface coating is preferably applied to the front board
face directly onto the smooth or textured surface at a rate that
results in a thickness in the final gypsum board product, also
referred to as the dry coverage thickness, in a range from about
0.5 mils. to about 4.0 mils. The application rate measured by
weight of the wet acrylic solution per unit area of the board
surface covered can be in a range of from 0.0054 grams/cm.sup.2
(0.18 oz. per square foot (oz./sf)) to about 0.045 grams/cm.sup.2
(1.45 ozs./sf). Ideally, the acrylic coating may comprise at least
in a portion thereof one or more rheology modifying compounds that
assist the coating in striking into the front face slurry surface
layer.
[0067] The features that are significant to the present invention
relate to the mixer 30 and the dispersion of the additives onto one
or both of the mats 14, 114 before they are assembled at the gypsum
board forming station. As shown in FIG. 1, and described in the
parent U.S. Pat. No. 6,524,679, the dense slurry layers 38, 138
which are deposited onto the mats 14, 114 before they are joined
with the core slurry layers 44, are first deposited on one or more
specified locations on the mats 14, 114 and then are dispersed
across the width of the mats 14, 114 by the rollers to provide a
uniformly thick film of dense slurry before they are joined at the
sheet joining station 80. This even layer of dense gypsum is for
the most part evenly distributed and for most additives, the
distribution of the additives within the dense slurry 38, 138 is
also evenly distributed across the mats 14 or 114 by virtue of the
dispersion of the additive within the dense slurry layer when it is
mixed into the dense slurry at controllers 36 or 136. However, for
certain types of additives, for example, hydrophobic additives, it
has been found that the mixture into the dense slurry is not always
even, but may result in clumps or uneven dispersion of the
hydrophobic additives throughout the dense slurry layer. As a
result, when the dense slurry is dispersed over the mats 14, 144,
the film of dense slurry may be evenly and consistently spread out
over the surface of the mat, but the additive itself may be
clustered, either randomly or periodically, on the mat. Such as
eventuality is undesirable, since uneven dispersion of the additive
on the surface of the gypsum board products often result in the
additive working poorly or inadequately to perform the function for
which it was added.
[0068] For example, one additive that was found to experience
inconsistent dispersion over the board surface was a wax emulsion.
The wax emulsion was added to provide desirable characteristics to
the board surface, for example, to enhance water resistance at the
board surface. However, as is generally well known, water will seek
to penetrate into a surface and will first succeed to do so at a
point of least resistance. Thus, water seepage into the core of a
board was facilitated by the uneven dispersion of the wax emulsion,
and the boards were found to not meet the exacting standards of
water resistance that were required in certain jurisdictions. Thus,
the features of the present invention were developed to provide for
more even dispersion of additives, and especially hydrophobic
additives, into the dense gypsum slurry and thus to provide a
consistently more even dispersion of the additive over the complete
width profile of the board.
[0069] Referring now to FIG. 4, in which similar elements are
identified by the identical reference numbers, the mixer 30 is
shown in a schematic diagram illustrating the additive delivery
system. Mixer 30 may take the form of any of a number of mixer
types, but in this instance, the mixer 30 preferably is a pin mixer
30 known in the art. The pin mixer 30 is the general mixer for all
slurry for both the dense slurry layer and the core slurry layers.
As described above, the core slurry 44 is taken directly from the
mixer 30 through the controller 46. However, the controller 36
controls the dense slurry 38 as it is siphoned from the pin mixer
30. The pin mixer 30 has an inlet aperture 186 connected to an
additive feed pipe 188 that feeds directly into the dense slurry
outlet 34. The pipe 188 is used for delivery of dense slurry 38 to
one or both of mats 14, 114 onto which dense slurry 38 or 138,
having the appropriate additives, is desired. Thus, the additive
feed pipe 188 is capable of introducing an additive directly into
the slurry stream as it passes through the dense slurry outlet
34.
[0070] Although shown being connected to only the one dense slurry
outlet 34, it should be understood that another pipe, similar to
pipe 188, may also be attached to other outlets, either of the
dense gypsum slurry, for example, outlet 134, or even to the core
gypsum slurry outlet 148, if that is found desirable. The described
structure is not to be limited to the single connection shown, but
a feature of the invention is the capability of targeting specified
additives to that gypsum layer where they are desired. Other
modifications will also become apparent to a person having ordinary
skill, for example, connecting the additive feed pipe 188 directly
to the controller 36 or 136, where the desired additives are mixed
into the dense gypsum slurry stream as other controls and processes
are simultaneously occurring.
[0071] Referring again to FIG. 4, the additive provided for mixing
into the gypsum slurry streams is contained in an additive
reservoir 192. Because the construction described herein is
especially well suited for even dispersion of wax additive, for
providing the desirable water absorption resistance at the surface
of the gypsum board. The reservoir 192 contains wax, and it may
require a preheating arrangement and a method of emulsifying the
wax into an emulsion that can be easily dispersed in an aqueous
slurry. The reservoir 192 schematically is shown being separated
from the injection port 186, but it may be patentable to provide
the reservoir closer to the pin mixer 30, of physically possible,
to maintain the wax in the emulsified condition prior to
delivery.
[0072] A transfer pipe 194 is connected at one end to the wax
emulsion reservoir 192, which provides a continuous stream of wax
emulsion to the injection port 186, as needed. Filtration of the
wax emulsion may be required, and a filter (not shown) may be
disposed in the transfer pipe 192 to avoid excessively large wax
solids from entering the wax emulsion stream to avoid plugging or
clogging the delivery system, as will be described below.
[0073] The transfer pipe 192 is connected at the other end to a
pump 198 that may include a flow control for regulating the
rotation of the pump 198, or as a separate flow control valve 196
disposed in-line in either the transfer pipe 194 or the additive
feed pipe 188, so as to control the rate of flow of the wax
emulsion additive to the injection port 186. The wax emulsion rate
flow control is a significant feature of the present invention, as
very low flow rates are required for the additive, so as to
maintain the desirable homogeneous consistency and constituent
ratio of the dense gypsum slurry to additive. This permits the
invention to achieve the optimum balance between reducing the cost
of unnecessary additive, while also simultaneously providing a
homogeneously applied water resistance, that is, consistently
reducing the surface absorption characteristics, across the compete
lateral surface of the board.
[0074] To achieve the desired purposes, another significant feature
is provided at the injection port 186, that mixes the additive into
the dense gypsum slurry as it is transferred from the pin mixer 30
to the top and bottom slurry coating stations 110, 18,
respectively. Thus, there is provided an additive delivery system
200, disposed in-line at the additive injection port 186 within the
end of the additive feed pipe 188 that is attached to and feeds the
dense slurry outlet 34. An added impetus beyond gravitational
forces for transferring the additive from the reservoir 192 to the
additive delivery system 200 is shown schematically in FIG. 4, and
comprises a pump 198, that may be a positive displacement pump, an
air diaphragm pump, or other appropriate pumping mechanism. Other
appropriate pumps comprise a MOYNO pump, available from Moyno,
Inc., of Springfield, Ohio or a TRIPLEX pump, available from Kerr
Pumps, of Sulphur, Okla. The positive displacement is necessary to
maintain a positive pressure on the additive stream to make it
available at the additive delivery system 200, when and as needed.
These types of positive displacement pumps are preferable because
they avoid shearing of the emulsion, and so maintain the emulsion
in the desired state.
[0075] Referring now to FIG. 5, two additive delivery systems 200
are each connected to an additive feed pipe 34 at separate additive
injection ports 186. Although two additive delivery systems 200 are
shown, any number from one to twenty such systems may be utilized,
depending on the amount and types of additives that is desired to
be added to the slurry stream in pipe 34. Each of the systems 200
includes a quick connect coupling 202 to enable the quick
connection to an input additive feed pipe, such as pipe 188 shown
in FIG. 4. The quick connect coupling 202 is prefabricated and is
attached to the system 200 and may include a quick connect hut 204
that provides a sealed fluid communication to the pipe 188 upon a
simple tightening of nut 204.
[0076] This arrangement provides for several advantages, including
that of selective and easy attachment of the appropriate additive
delivery system 200 to the dense gypsum slurry stream, depending on
the type and characteristics of the board desired for manufacture.
Alternatively, and in view of the below described construction of
the system 200, it may be appropriate to connect two or more
systems 200 to the same feed pipe (not shown), thereby delivering
twice the amount of slowly injected additive into the slurry
stream. This alternative procedure may be utilized to avoid
excessive flow rate that would flow through a single system 200,
and would also ensure more complete mixing of the additive in the
gypsum slurry.
[0077] As shown in FIGS. 1, 4 and 5 first gypsum slurry outlet pipe
34, connected to the pin mixer 30, and extends in an outward
direction therefrom. After being discharged from the controller 36,
it is connected to a first input pipe 208 that may be utilized as
an extractor for dense slurry from the slurry stream, in the event
such slurry is desired, for example, for testing or quality
control, or if necessary for some other process in the manufacture
of the gypsum board panels.
[0078] Downstream along pipe 34 a diaphragm pinch valve assembly
210, comprising a connecting joint 212 connecting to the pipe 34 at
one end, a diaphragm pinch valve 214 at the other end, and a
central section 216, to which an air supply port 218 for the
diaphragm pinch valve 214 is connected. The diaphragm valve 214 is
pneumatically driven by the air supply and can control flow rate of
the dense gypsum slurry as it passes through pipe 34.
[0079] Immediately downstream of the diaphragm pinch valve assembly
210 there are disposed the two additive delivery systems 200, but
fewer or more of these systems 200 may be connected to the pipe 34.
Although, the preferable configuration of downwardly flowing
systems 200 are shown, in order to be assisted by gravity flow of
the additive, it is contemplated that this orientation may be
changed to conserve space, and the systems may be disposed at an
angle to the vertical or even underneath the pipe 34.
[0080] The wax emulsion additive providing in the reservoir 192
(FIG. 4) may be any of a variety of waxes capable of providing
water resistance to the surface, for example, one or more of a
paraffin wax emulsion or other known and commercially available
materials capable of providing water resistance characteristics.
Furthermore, although described above in terms of the use of these
additives with a fiber mat faced gypsum board, the present
invention may also be used together with standard paper faced
gypsum to increase the water resistance characteristics at the
gypsum paper surface interfaces of such boards, or other types of
cementitious boards in which targeted delivery may enhance the
value of the products. Other additives that can be utilized in this
method for both the types of panels described in aforementioned
U.S. Pat. No. 6,524,679 and for paper face products and any
combination of cementitious and paper to improve or enhance other
properties are as follows: polymers, boric acid, borates, other
intumescence-like additives, surfactants, dispersants, retarders,
potash, silicates, starches, phosphates, perlite, alumina and any
material that can be solubilized or dispersed in a liquid media may
be used.
[0081] Referring now to FIGS. 6 and 7, perspective views,
respectively, of a ready to deploy and of a deployed additive
delivery system 200, shown in alternative embodiments. As shown in
FIG. 6, system 200 includes the quick connect nut 204 for
connecting additive feed pipe 188 to the additive inlet port 186.
With this quick connect, a user may easily exchange pipes for
providing other alternative additives, as desired, for injection
into the dense slurry stream.
[0082] For example, a wax emulsion additive has been described
above. However, other chemical additives may be desired to be added
by targeting only one of the layers of gypsum. Also physical
additives may also be added for providing other desirable
characteristics, for example to the dense slurry layers. One such
exemplary additive may comprise the targeting of microfiber to the
stratified dense slurry layer for providing enhanced structural
strength to the outer layers of the finished gypsum board product.
Alternatively, the microfibers may be introduced to both the dense
and core gypsum layers, but in different concentrations, e.g., more
concentrated mixture of microfibers may be added to the dense
slurry layer and a less dense concentration may be added to the
core gypsum, utilizing the teachings and structural features of the
present invention.
[0083] The microfibers may comprise any of a number of different
materials, for example, e-glass, carbon, mineral fiber, polymeric
and/or metallic fibers and the concentrations may be varied,
depending on the specific characteristics of the gypsum layers that
are desired. An appropriate range of concentration of such
microfibers may be between 0.1% to 5.0% by volume. The microfibers
may have lengths of from between 1.0 and 25.0 mm, widths of between
0.002 and 0.025 mm and an aspect ratio of between 1:1 and 25:1,
depending on requirements.
[0084] Referring again to the system 200 shown in FIGS. 6 and 7,
once the quick connect coupling nut 204 is tightened on to the
system 200, there s a sealed flow of the additive materials, for
example, a wax emulsion, through the system 200 and into gypsum
slurry pipe 234. The system 200 thus includes structural features
that control the consistency and dispersion of the additives within
the slurry stream passing through pipe 34, as described above.
[0085] Additive delivery system 200 comprises an enclosing housing
206 that is shown as a rounded conical housing having a large
diameter opening 208 and a small diameter opening 208 and a small
diameter opening 209. The small diameter opening 209 is connected
by the quick connect pipe 204 to the additive feed pipe 188, and
provides fluid communication so that the additive may flow through
the housing 206 toward the inlet port 186. Although shown as having
conical shape, the housing 206 may take any type of shape
commensurate with maintaining the flow of additive into the slurry
stream 38 in pipe 34, for example, an oblong bow or an octagonal
enclosure.
[0086] Housed within the enclosing housing 206 is a turbulator 220
that extends beyond the large diameter opening 208 in a
longitudinal direction, as shown. The turbulator is fixed as shown
in FIG. 6. It should be noted that FIGS. 6 and 7 drawing may not
necessarily be to scale. The turbulator 220 is a feature of the
invention that assists in homogeneous blending at the injection
point of the additive into the slurry stream. The additive feed
system 200 includes two insertion/retraction handles 222 that
provide the controls for the longitudinal position of the
turbulator 220, so that when in the undeployed position as shown in
FIG. 7, the handles extend radially outwardly to disconnect the
turbulator 220 from the receiving neck 234. Pulling the handles 222
toward the housing 206, as shown in FIG. 6, locks the turbulator
220 in a direction away from the smaller diameter opening 210, and
when connected within the system 200, toward the additive injection
port 186. Pulling said handles in locks the coupling into position,
connecting the housing 206 to receiving neck 234. In this position,
tubular constrictor valve 224, injector nozzle 226, and additive
outlet opening 228 extend into receiving neck 234 and position the
turbulator 220 for desired delivery of additives. The turbulator
220 comprises a tubular constrictor valve 224, which is attached to
an injector nozzle 226, having an additive outlet opening 228 at
the distal end thereof. The inner diameter of the injector nozzle
226 may be in a range of from about 3/32) to about 3/16 of an inch
(2.38 to 4.75 mm), and preferably is about 1/8 of an inch (3.17 mm)
in diameter at the opening 228. The additive outlet opening
preferably has an internal opening diameter that is much smaller
than that of the injector nozzle, and may be in a range of from
about 3/32 to about 1/16 of an inch (2.38 to 1.59 mm).
[0087] The above-described configuration provides egress of wax
emulsion solids at an appropriate flow rate into the dense slurry
layer of between 1 lbs./Msf to about 10 lbs./Msf where Msf is one
thousand square feet. The turbulator delivery pattern, that is, the
spray of additive that is delivered to the dense gypsum slurry 38
may comprise one or more known patterns that can provide the
maximum dispersion of the additive material within the slurry
stream, for example, a flat, conical multiple linear injection, or
other appropriate geometrical pattern capable of injecting the
additive materials deep into the slurry stream so as to effectively
mix them thereinto. Thus, although shown having a cylindrical
delivery tip in FIG. 7, the delivery tip and additive injection
opening 228 may take other founds to provide a different delivery
pattern and thereby to achieve optimal additive homogenization in
the slurry stream.
[0088] The angle of injection also provides a variable additive
injection parameter that can be optimized for obtaining maximum
additive penetration and homogeneity of additive in the slurry
stream.
[0089] That is, while the angle shown in FIG. 7 is directly
perpendicular to the plane of the end opening 208 of the housing
206, other injection angles can be used as well, and may take on
either an acute angle relative to the direction of slurry flow, and
may be either angled with or against the flow in a range of from
about 1.degree. to about 179.degree. relative to the direction of
flow. Optimally, the angle is very close to perpendicular as shown,
but practical adjustments in a range of from about 70.degree. to
about 110.degree. possibly provide desired mixing effects of the
additive materials as these are delivered into the slurry stream.
For example, an angle which injects the additive into the stream at
an angle against the flow of the fluid stream so that the mixing
occurs more vigorously. However, this may not be desirable in some
instances, for example, if it is not desirable to inject the
additive material counter to the slurry stream so as to avoid
excessive agitation or to avoid disturbing the slurry flow. In such
a case, it may be preferred to angle the additive injection
direction with the flow of the slurry stream and have the additive
be mixed into the slurry by natural agitation during delivery and
spending of the dense slurry 38 over the mats 14, 114 or
alternatively, over paper facing.
[0090] The turbulator 220 has not been generally utilized for
providing additive injection into the slurry of a gypsum board line
during the manufacturing process of gypsum board. Thus, although
such turbulator nozzles are available commercially, for example,
from Spraying Systems, Co. of Wheaton, Ill. available as Part No.
1/8HH-SS8W, these types of turbulators have not been made nor used
for dispersion of additives directly into a flowing slurry stream.
The aforementioned U.S. Pat. No. 4,378,405 to Pilgrim, for example,
teaches a surface modifying additive such as water-proofing agents,
in the form of synthetic resins, to be sprayed onto the glass mat
fabric or web, but this suggestion does not necessarily result in
the desired additive on the surface of the gypsum board product,
especially if the mat is essentially encased in the gypsum, as is
taught in the aforementioned parent U.S. Pat. No. 6,524,679. Others
teach the dispersion of the additive in the core gypsum slurry as
well as the surface layers in equal propositions, thus failing to
provide the targeted additive delivery to specific layers.
[0091] As an example of the targeted delivery of the wax emulsion
additive described above, it has been found that mixing a first
batch of additive to the gypsum slurry mixture in pin mixer 30 in
the ration of, for example, 60 lbs./Msf additive wax emulsion per
batch of slurry mixture, and adding 5 lbs. additional wax emulsion
directly to the dense slurry mixtures 38, 138 at the pipes 34, 134,
as described above, will result in lesser water resistance
characteristics in the core layer, but in much greater water
resistance in the two surface layers of gypsum that encase the
fiber mats 14, 114, because of the smaller proportion of dense
slurry to core slurry that is delivered to the gypsum board line.
This results in a product that is lighter in weight, and is
significantly better able to repel water or moisture from the
surface layers, where this property is most needed, than is, a
standard, non-targeted process that would utilize additive in the
amount of 70 lbs. per batch evenly spread across all three
layers.
[0092] Referring again to FIGS. 6 and 7, the configuration shown
provides for the tip 2 of nozzle 226, including additive outlet
opening 228, to be flush with the inside wall of the pipe 34. In
this way, the turbulator 220 does not disturb the slurry stream,
but nevertheless injects the additive (wax emulsion) into the
slurry 38 as it is transported therethrough. Because of the
continual fluid pressure provided by the pump 198, a vortex of
additive wax emulsion is produced in the slurry stream which
ensures more even mixing. Moreover, use of a positive displacement
pump, so as to avoid pulsations in the additive delivery, produces
more even mixing results.
[0093] However, the position of the nozzle tip may also be more
actively disposed to extend beyond the inner surface of the wall of
the pipe 34, and the additive outlet opening 228 is disposed in the
slurry stream and so to inject the additive more forcefully into
slurry mix to obtain a more robust mixing. However, care must be
taken to avoid damage to the nozzle 226, since the gypsum slurry is
being transported very rapidly through the pipe 34. This
configuration may be used together with the angled nozzle,
described above, in which the nozzle tip is angled at an acute
angle with the flow of the gypsum slurry, so as to minimize the
risk of damage.
[0094] The quick connect coupling 210 is attached at the narrowed
209 of the housing 206 to the nut 204, and at the distal larger end
208 to the receiving neck 234, shown as a hexagonal housing, but
capable of being almost any geometrical shape. When attaching the
additive delivery system 200, care must be taken so that the nozzle
226 is not damaged. Once the housing 206 is in place and engaged
with the receiving neck 234, the handles 222 are rotated in the
upward direction, which locks the system in place. Simultaneously,
the locking action of the handles 222 also extends the nozzle 226
downwardly toward the pipe 34 until the nozzle additive output
opening 228 is flush with the inner wall surface of the pipe 34.
The port 186 is enclosed by a port enclosure 236 that is connected
onto the pipe to hermetically seal the port 186, preferably by
welding or other appropriate means. An optional nut 238, and a
transitional pipe connector 239 are shown in FIG. 6, but these are
not necessary if a dedicated additive port 186 is provided in the
gypsum board line.
[0095] Additional modifications are also possible in the event that
a dedicated additive outlet port 186 is provided. For example,
vanes (not shown) or other means may be attached to the inner wall
of pipe 34 or to the end of the nozzle 226, for directing the flow
of gypsum slurry around the outlet port 186 so as to avoid fluid
pressure of the moving gypsum slurry stream being directed onto the
nozzle, which because of its shape and size may be then better able
to withstand that pressure.
[0096] It is advantageous and preferable that the additive be
applied within the dense gypsum slurry so as to avoid further
dispersion thereof, for example, if the additive were simply
sprayed over the surface. In such an example, the water film
provided over the surface of the gypsum board at the point in the
gypsum board formation process, known in the gypsum board industry,
may further disperse the additive if applied on the surface only.
At this point, there is a measure of control that can be provided
over the board manufacturing process by introducing formulation
additives to increase or decrease the speed of recrystallization of
the gypsum form solution or slurry form, Ideally, either the
polymer additive or the wax emulsion in the gypsum slurry solution
may be used to enhance the bonding strength also between the core
slurry 44 and the outer surface dense slurries 38, 138 and between
the dense slurry that extends across and through the mats of the
glass fiber facing sheets 14 and 114'. The polymer may be
generating a polymer matrix that extends from the junction of the
lower density core slurry and into the dense slurry layers 38, 138,
which have penetrated through the sheets 14, 114, and to extend to
the gypsum board surface. The polymer matrix is effectively
embedded within the gypsum base and provides a coalescing surface
upon which further finishing can be based, e.g., painting or a
water impervious acrylic cover, that may be added at this stage of
the finishing process, for example, by spray coating.
[0097] The surface texture of the front face of the completed
gypsum board may additionally include these additives, which as a
part of the underlying matrix, help present a smooth dense layer of
gypsum to which other polymeric, e.g., acrylic, compounds can
adhere. As the dense slurry layer cures, for example, in the drying
process, it hardens to provide a stiff surface capable of retaining
a load and repelling water. The surface having the polymer
additive, improves water resistance and the other additives may
provide specific sites for chemical adhesion by other polymers. The
composition of a water resistant or impervious coating can
additionally comprise one or a combination of the following
polymeric compounds: polyacrylamide, polymethylacrylamide,
polyvinyidene chloride (PVDC), polyamide, poly (hexamethylene
adipamide), polyvinylchloride (PVC), polyethylene, cellulose
acetate, polyisobutylene, polycarbonate, polypropylene,
polystyrene, styrene, butadiene, styrene butadiene copolymer,
polychloroprene, styrene, butadiene (Neoprene.RTM.), natural
rubber, poly (2,6 dimethyl pentene oxide), poly
(4-methyl-1-pentene) (Teflon.RTM.), natural rubber, poly (2,6
dimethyl pentene oxide), poly 4, methyl pentene-1 and polydimethyl
siloxane, and may be used in either or both of the dense slurry
layers, and in different concentrations even in the core gypsum
layer.
[0098] Testing of the gypsum board products comparing those with
the wax emulsion additive and those without, revealed a significant
increase in water resistance, especially when utilized with other
water resistant additives in the core and modified dense gypsum
slurry layers. The testing results of samples indicate an average
increase in water resistance of at least 300%, and certainly,
meeting and exceeding the minimum requirements and standards
promulgated by the Canadian Construction Materials Center. The data
appears to provide support to the theory of better dispersion
across the complete surface of the board, thereby enhancing
performance of the surface of the dense slurry layer. Additional
benefits may be obtained by varying the wax emulsion or other
compounds used, or a combination of compositions, or varying other
parameters such as the solution strength, the application rate and
the time and condones of curing, so as to increase the final gypsum
board product's water resistance and other desirable
characteristics.
[0099] This invention has been described with reference to the
above-disclosed embodiments. Modifications and alterations of the
disclosed embodiments are within the ability of persons having
ordinary skill in the gypsum board art, and this invention is not
intended to be limited to the description of the disclosed
embodiments, the invention being limited only by the following
claims and equivalents thereof.
* * * * *